The present invention relates to an apparatus for sealing a pipeline section to prevent fluid flow through the pipeline and, alternatively, to clear obstructions in the pipeline. More particularly, the present invention relates to a pipe sealing apparatus that is insertable in pipelines of varying diameters and inflatable therein to seal a pipeline section. Such a pipe sealing apparatus is commonly referred to as an inflatable plug.
Inflatable plugs provide a quick and ready means to mitigate the uncontrolled release of fluids from a pipeline when a break occurs in the pipeline. One or more inflatable plugs may be used to isolate the break from the rest of the pipeline or isolate fluids held in the pipeline from the area of the break. Inflatable plugs are particularly helpful in the handling of liquid waste emergencies. For example, in the event of a liquid waste spill, inflatable plugs may be situated at the various surface entry points of a sewer system to prevent the liquid waste from escaping a designated containment area.
Inflatable plugs are also used to isolate sections of a pipeline when performing routine repair or maintenance on the pipeline. When replacing a valve, for example, a plug may be inserted into the pipeline upstream of the valve to thereby isolate the valve from the pipeline system and to allow for removal of the old valve. Inflatable plugs may also be used with existing pipeline valves to safely isolate an area where hot work is to be performed.
One type of inflatable plug is described in U.S. Pat. No. 4,565,222, which is assigned to the assignee of the present invention. The inflatable plug described there includes an inflatable bag of flexible sheet material that is constructed to form an elongated cylinder. The ends of the inflatable plug are wrapped around rigid end supports and then metal collars are placed over the ends of the inflatable plug. The metal collars are swaged or clamped down to form a fluid tight seal between the end supports and the collars. One of the rigid end supports includes an open pipe connectable to a pressurized air or water supply. The plug is inserted into the pipeline in the deflated state and maneuvered into the desired section of the pipeline. Pressurized air or water is then delivered through the open pipe to fill the inflatable bag. The inflatable bag expands to fill the pipeline section and frictionally engages the inside wall of the pipeline section, thereby sealing or plugging the pipeline.
Another type of inflatable plug may be used to clear a blockage inside a pipeline as well as to seal the pipeline. Such an inflatable plug is commonly referred to as a flow-through type inflatable plug. An example of a flow-through inflatable plug is described in U.S. Pat. No. 5,353,842, which is also assigned to the assignee of the present invention. The inflatable plug shown there includes an elongated cylinder with a central, longitudinal bore and an expandable covering surrounding the central cylinder. The expandable covering is comprised of an elastomeric material which is wrapped around the cylinder. At one end of the inflatable plug, a first fluid inlet is provided for delivering pressurized air or water between the outer surface of the cylinder and the inner surface of the covering and a second fluid inlet is provided for delivering pressurized fluid to the cylinder bore. When the plug is inserted in a pipeline adjacent a pipe blockage, the first fluid inlet is used to inflate and expand the space between the covering and the cylinder, such that the outer surface of the plug sealingly engages the inside surface of the pipeline section. Then, pressurized fluid is delivered through the second fluid inlet and into the cylinder bore. This pressurized fluid is discharged at the opposite end of the cylinder bore in the direction of the pipe blockage, thereby clearing the blockage from the pipe.